What is 100LL?
100LL, also known as 100 octane aviation fuel (100 Low Lead), is a petroleum fuel designed for reciprocating aircraft engines. This gasoline has an octane number of no less than 99.6, adheres to ASTM Specification D 910, and contains tetraethyl lead as an anti-knock agent. The addition of tetraethyl lead (TEL) in aviation gasoline also requires the addition of ethylene dibromide (EDB) as a scavenger to help remove lead oxide from engine components after combustion. The resulting emission product is mostly a lead dibromide particulate which enters the atmosphere and pollutes the environment with lead. Unlike other pollutants, this compound is never absorbed or reacted into something less harmful.100LL has been the mainstay in general aviation for the past thirty years. Prior to environmental pressure thirty years ago, the TEL concentration in general aviation fuel was double what it is today (0.53 mL/L). 100LL is being scrutinized again today by various environmental groups, as it is currently the source of 45% of annual domestic lead emissions. On October 12th, 2006, a petition was filed with the EPA by Bluewater Network, a division of Friends of the Earth, asking the EPA to determine whether lead emissions from general aviation pose a significant risk to human health. If sufficient information was found, the EPA was asked to make a formal Finding of Endangerment to public health and welfare. This would result in the regulation of lead emissions caused by the combustion of 100LL. The other driving force behind the reduction of 100LL use is the updated National Ambient Air Quality Standard (NAAQS) for lead, which was released by the EPA in October 2008. For the previous twenty nine years, the limit for ambient air lead was set at 1.5 µg/m3. Medical research since then has shown that much smaller lead levels can cause serious health effects, especially in children. The new standard allows for lead levels to be reduced to only 0.15 µg/m3 of air, or 10% of the old standard, by no later than January 2017.